Etching process



Jan. 7, 1936.

R. A. ZARSE ETCHIIjG PROCESS Fild April 25, 1933 NEW METHOD NO DOT DOT n01- DOT STAGINGCCOPPER) M I WI v l I I r [In H l I 7 Hui? :SNHAETE? \H W1" fsiwssfisssssm DOT DOT D01- OLD METHOD' sTA6|Ne(coPPER) A. h /;l:

B05 e 7 14, Z 0/176 INVENTOR ATTOR N EY Patented Jan. 7, 1936 UNITED STATES PATENT OFFICE The invention relates to an etching process and more especially to a still process for etching copper only.

The present etching for the manufacture oi. half-tones for printing for newsapper or other publications is carried forth by mechanical or photochemical processes and these involve the use of a solution including chloride of iron and nitric acid, the mechanical process requiring the splash, spray or agitation of the solution on the plate surface or electrolytic etching where the electric current is the mordant and the first bite or etch is given to secure printing depth, this requiring a number of seconds to approximately ten minutes, whereupon such plate is washed and dried and magnesium carbonate is rubbed into the etched part that the work may be made visible for staging. The darkest tones are painted over with a fine brush using paint or ink as an acid resist, then the plate is given a number of stages of etching to produce the lighter tones, while the balance of the plate continues to etch. After staging the paint is removed and the lighter tones are re-etched locally to reduce the dot formation. method of etching requires considerable, time for the staging and the finished product, regardless of care in workmanship, thus being a mechanically finished and not a natural reproduction of the original copy.

It is the aim of the present process, which involves the use of. a solution consisting solely of chloride of iron and common salt or sodium chloride, whereby increased production at a minimum cost is had, while the etch will be from one to three times deeper than any known process and also the product will be absolutely clean for printing to make a perfect reproduction and at the same time eliminating staging as well as the use of mechanical devices or present day etching machines. 7

Further this process eliminates the use of rosin to make deeper impressions or rough etchings and. the darkest tones will etch to a certain depth at which they will vacate, this resulting from the sediment released by etching the copper remaining in the etched area and as the etching is continued the next lighter tone of the picture will be held by such sediment as well as each color value held to its correct tone by an overhang at the working face' of the form and in this way the lightest tone will reach the maximum depth possible of etching, reducing the dot for the lightest tones to a pin point. By the use of the solution which is of non-acid characteristic there is pre- This present served the enamel shell throughout the etching process, this enamel shell being at the working side of the form and in rinsing to preserve the sediment collected in the cavities of the darkest tones etched and additionally the artificer is not placed in an unhealthy status, he having time to relax, stand or walk during the etching period.

In practicing the process it is essential that a solution of chloride of iron and common saltor sodium chloride be used which is entirely free from acid and the portions of this substance may be varied and the dissolving thereof in water, the quantity of the latter being variable.

The solution is introduced into a container to have a depth of approximately one inch, it being found that the desirable solution has the proportions of approximately one gallon of chloride of iron (35 degrees to 40 degrees Beaum) to three ounces of salt or sodium chloride. The contained solution has introduced thereinto the form or copper plate, it being understood of course that such plate is cleaned prior to the submersion thereof into the solution and it is suspended face downward to about one-half inch of the bottom of the container. This plate remains in suspension for about three minutes within the solution and then is removed therefrom and rinsed under a slow flow of water for a few seconds and again placed into the etching solution and allowed, as before, to etch for about three minutes. Then the'plate is again rinsed and this procedure of etching and rinsing is continued until the plate is completely etched.

Referring to the accompanying drawing:

Figure 1 is a sectional view through a form as operated upon under the process constituting the present invention.

Figure 2 is a similar view showing a form as etched under the present day or old method.

Referring particularly to the drawing, A desig- 4 nates generally the copper plate and B the enameled facing thereto, while 5, 6, 1, B and 9 re-- spectively are the relief dots created under both the old or present day and the new process and H) and l I respectively are the cavities of the etch in the forms disclosed by Figures 1 and 2 of the drawing. v

The enamel face B is created by ink or a substance involving .a determined amount of fish glue and egg albumen and the thickness there- 5 7 of may vary as in some instances it is heavy and in others thin. Now when the form A is placed in the solution of the chloride of iron and sodium chloride or salt the sediment l2 released in the cavities l0 caused by the solution etching the copper will deposit in such cavities and thus constitute a barrier or resist the etching at the localities of deposit and in this manner where the sediment remains in the etched dot of the darkest tones it stops the etching and holds that tone natural and as the plate continues to etch the next tone and the next and so on are held back, preserving those tones to a natural likeness and as a result there are no abrupt difierences of tone values as are sometimes had by staging. By reason of the non-acid characteristic of the solution involving the sodium chloride or salt and chloride of iron, a preservation of the enamel face B is attained throughout the etching process, the sodium chloride or salt when mixed with the chloride of iron insuring a neutral nonacid solution.

It should be apparent that smooth edge etching efiect is attained under the process herein before described and constituting the present invention and also that a deep etch is had and staging entirely eliminated. Under the present or old method, when you consider a worker using a fine camel hair brush and painting over a plate to hold back certain tones, it takes a steady hand and demands quite a strain on the eyes. To do this staging the plates are brushed each time and the enamel shell removed Where the dot had been etched away from beneath, etching the color tones considerably lighter and comparing color for color of the copy reproduced and in many instances the hand of the operator is unsteady and the eyes not keen to tone qualities, with the result that inferior etching is accomplished, so under the process constituting the present invention these factors are nil.

What is claimed is:

1. A process of etching copper printing forms. consisting in covering said forms throughout the face to be etched with an enamel and etching said face with a mixture consisting solely of sodium chloride and chloride of iron.

2. A process of etching metal printing forms having enamel coatings on the surface to be etched, consisting in introducing the said forms into a mixture of a solution containing approximately one gallon of chloride of iron and approximately three ounces of sodium chloride.

3. A process of etching a copper printing form 20 consisting in covering the face of the form to be etched with an enamel, subjecting said face for a predetermined period of time to the action of a mixture consisting solely of sodium chloride and chloride of iron, rinsing said face, and again subjecting said face to the action of said mix-- ture without removing any portion of said enamel.

ROBERT A. ZARSE. 

